家蚕丝素酶fibroinase的结构解析及其活性周期性变化的分子机制

丝腺作为家蚕(Silkworm, Bombyx mori)唯一的泌丝器官，是整个蚕丝产业的生物学基础。在每龄的幼虫期，丝腺腔中的丝蛋白都要经历从降解（眠期）到重新合成的过程。可见丝腺腔内丝蛋白的降解是丝腺发育的一个关键环节，它为丝腺的下一个发育周期的提供了信号。前期研究工作表明丝素酶fibroinase通过其活性的周期性变化控制着丝腺腔内丝蛋白在眠期和预蛹期的降解过程。然而，在丝腺发育过程中调控丝素酶活性周期性变化的因素和机制并不清楚。本课题将围绕着丝素酶的活性调控这条主线，研究丝素酶的三维结构与酶活的关系；并从分子水平研究丝素酶基因的转录调控，探讨丝素酶的表达量与其活性周期性变化的关系；并通过研究丝素酶的生理抑制剂，找到丝素酶和抑制剂的拮抗关系，阐释抑制剂对丝素酶活性周期性变化的影响。最终阐明丝素酶在丝腺发育过程中参与的调控作用，构建丝腺发育过程中的丝蛋白稳定/降解的调控网络。

Silk gland of silkworm is a specific organ for secreting silk and is the biology foundation of the sericulture. In the larval stage, the development of the silk gland shows a cyclical process. At each molt period in early larval instars and the early pupa, the silk gland undergos a critial step that the digestion of fibroin and sericin in the lumen contents of silk gland. Several evidences demonstrated that the cyclial expression of fibroinase regulated the degradation of fibroin and sericin in the lumen contents of silk gland at each molt period in early larval instars and the early pupa. To understand the regulational mechanisn of the cyclial expression of fibroinase, we choose the fibroinase as the research target. We will determine the structure of fibroinase and clarify the structural basis of the digestion of silk proteins. By means of structural biology, we sought to determine the structures of fibroinase and clarify the structural basis of fibroinase to accommodate the silk proteins. Moreover, the gene expression profiles and the transcriptional regulation of fibroinase gene will be performed to study relationship between the expression level of fibroinase and the cyclial expression of fibroinase. Furthermore, the physiological inhibitor of fibroinase will be identified by biochemical experiment and proteomic tools, which could enable us to clarify the biochemical roles of inhibitors and fibroinase. Finally, our structural and biochemical observations will provide insights into the precise mechanism of the cyclial expression of fibroinase in regulating the digestion of silk proteins in the silk gland.